A shock absorber or damper is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy. Most shock absorbers (dampers) are utilized with external springs (coils).
Various devices for absorbing shock for vehicles have been attempted utilizing a piston rod moving up and down in a cylinder to provide oscillation dampening (“twin-tube” configuration) therewithin to provide smoothing of shocks that would otherwise be passed to the vehicle. Other shock absorbers utilize a floating piston which accommodates the volume of the piston rod as it moves in an out of a cylinder (“mono-tube” configuration). Such devices typically rely upon springs, most typically coil springs disposed around the body of the shock absorber, or in another location of the suspension, to carry the load of the vehicle. In one prior device a spring is required to internally control a valving operation, wherein fluid within the body of the shock absorber flows in an opposing direction to the motion of the floating piston back through a two-way valve, as gas in the gas chamber decompresses or compresses in response to external circumstances, and pressure in the fluid chamber lessens or increases to restore equilibrium within the system. However, the load is only partially sustained by the compressed gas therewithin and thus the device is effectively non-load-bearing without a spring working in concert.
It is further desirable that a shock absorber be capable of being adjusted to provide the desired “ride” characteristics. This is also important in making a shock absorber that can be adapted to a variety of vehicles. One device approaches this problem by teaching a shock absorber with an adjustable lock-out valve and two stage flow restriction. This suspension/shock combination device works in part by having fluid flow from a fluid chamber into another chamber during the compression and rebound strokes of a piston. The fluid flow is controlled through valves that can be manipulated externally to open and close on demand. By adjusting the opened and closed positions of the valves (or an intermediate position between opened and closed) fluid flow could be increased or decreased and therefore shock absorption characteristics are affected. This device is a damper only for lightweight vehicles such as bicycles. Further, this device does not support the vehicle's weight.
Yet another device teaches pneumatic connections for vehicle suspensions, but comprises a damper only. This device includes a piston inside a housing, wherein separate first and second chambers are also disposed. The piston includes at least one aperture, which regulates the flow of dampening fluid between the two chambers, having an affiliated actuator attached. Upon activation of the actuator, the piston aperture will be obstructed, thereby reducing fluid flow immediately. Deactivation of the actuator will once again permit free fluid flow. Further a frit restricts flow of fluid to assist in dampening shock impact.
Another device teaches a telescopic suspension device for vehicles having two liquid chambers interconnected by a conduit in which a valve unit is interposed. This device has a valve-within-tube structure. Flow of fluid is directly between outer tube and piston (or inner) tube. There is no stationary tube. Further, the valve body is located on the piston tube and thus moves with the piston tube. However, this device lacks adjustment control, although it does provide springless operation.
In another design, the damping tube is threaded to the bottom of the outer tube and the valve is externally threaded on the damping tube. This device requires that the damper tube have holes therein, and further requires a spring to support the vehicle. As an option, this device comprises a port that can be drilled on the outside of the damping tube, to fill same with gas so in extension the gas creates a negative biasing effect. However, no biasing effect is created in compression.
Most dampers in the market (either twin tube configuration or mono-tube configuration) have a gas chamber area, and, in the case of the mono-tube configuration, a floating piston. However, the gas chamber's purpose is not to provide spring action but is rather a place to accommodate the extra oil displaced by the piston rod as it moves down (compression). In another words, the force created in the gas chamber is not enough to sustain the vehicle's weight; hence, the need for an external spring for such dampers. The flow valve located at the end of the piston rod regulates the flow, hence, the damping.
Therefore, it is readily apparent that there is a need for a shock absorber that can provide the necessary operation range of damping motion without requiring that a spring be utilized in combination to support the load of a vehicle, and that further provides a biasing effect in both compression and extension.